Preheat the oven to 450 degrees F. Shred the zucchini with a cheese grater. Squeeze out as much water as possible. In a large bowl, measure 4 cups of shredded zucchini. Stir in mozzarella cheese, oregano, egg, salt and pepper. Lightly spray a 12-inch pizza pan with cooking spray. Spoon mixture onto pan to form a 1/2 inch high crust. Bake 15 to 20 minutes, until mixture is set and slightly browned, being careful not to burn. Chop half of a red onion and the tomatoes into small diced pieces. In a small bowl, mix together the olive oil, minced garlic and fresh rosemary. Spread the mixed toppin evenly over the baked crust. Spoon onion and tomatoes over the pizza. Bake an additional 10 minutes or until curst is crisp or becomes slightly brown. Remove from oven; sprinkle paresan cheese over the top and serve.